The present invention relates to a thermo-electric cooler for use in an optical assembly.
Optical assemblies of the type supported on an optical bench and comprising one or more components such as lasers, lenses, filters, isolators and waveguides, are sensitive to movement variation. One of the causes of movement is temperature tracking. The term, xe2x80x9ctemperature trackingxe2x80x9d is used to refer to a temperature dependent variation in the output signal of an optical assembly as a direct result of the movement of components in the optical assembly due to thermal expansion and contraction. This problem is particularly severe for optical assemblies in which the length of the xe2x80x9coptical trainxe2x80x9d is significant; for example, where there are a plurality of optical components positioned in series along the optical bench.
An aim of the present invention is therefore to minimise the impact of temperature tracking for optical assemblies.
Previously, thermo-electric coolers have been used to maintain the top-surface temperature of an optical bench within a certain range. These thermo-electric coolers operate by pumping heat towards or away from the required surface using the Peltier effect. However, although thermo-electric coolers are operable to maintain optical bench temperature they are themselves still sensitive to temperature tracking. In the situation that there is a temperature gradient between the top and bottom surfaces of a thermo-electric cooler the cooler itself begins to deform. Because an optical bench is typically supported on the top surface of a thermo-electric cooler this leads to deformation of the optical bench itself and as a result performance of the optical assembly is affected.
Previously a non-compliant (high tensile modulus) layer has been used on top of the top surface of a thermo-electric cooler. This stiff layer, seated on the thermo-electric cooler acts with brute force resistance to prevent the thermo-electric cooler from bowing, thus minimising the actual magnitude of deformation. However, this method does not actually prevent deformation from occurring it merely works to minimise the resulting effects.
Another object of the present invention is therefore to provide a thermo-electric cooler which overcomes or at least mitigates one or more of the problems mentioned above.
Further benefits and advantages of the invention will become apparent from a consideration of the following detailed description given with reference to the accompanying drawings, which specify and show preferred embodiments of the invention.
According to an aspect of the present invention there is provided a thermo-electric cooler for use in an optical assembly said thermo-electric cooler comprising:
a surface arranged to provide support for at least part of an optical train in use, said surface being divided into a plurality of regions separated by gaps.
This provides the advantage that each region of the surface has a xe2x80x9cneutral regionxe2x80x9d in which deformation as a result of temperature variation is minimal. By dividing the surface into regions, more of these xe2x80x9cneutral regionsxe2x80x9d are available.
In a preferred embodiment, a thermally conductive layer substantially covers the surface including the gaps. The thermally conductive layer covers the surface and enables heat to be transferred effectively between the regions.
In one embodiment the surface is arranged to indirectly support at least part of the optical train. That is, optical components do not have to be directly supported by the surface of the thermo-electric cooler, although that type of direct support is possible.
Preferably the regions in the surface are of substantially the same size and shape. This provides the advantage that the xe2x80x9cneutral regionsxe2x80x9d of each region of the surface behave in substantially the same manner.
Preferably the thermally conductive layer is also compliant. This is advantageous because the thermally conductive layer is then able to cope with deformation in of the thermo-electric cooler.
Advantageously, the thermo-electric cooler comprises only one temperature monitor.
In one embodiment the thermally conductive layer comprises graphite sheet and has a thermal conductivity greater than about 600 W/mK.
Preferably the thermally conductive layer is arranged to protrude into each of the gaps. This is advantageous because more xe2x80x9cslackxe2x80x9d is provided in the thermally conductive layer which can be used when substantial deformation of the top surface of the thermo-electric cooler occurs.
The invention also encompasses an optical assembly comprising a thermo-electric cooler as described above.
According to another aspect of the present invention there is provided a method of manufacturing at least part of an optical assembly comprising:
dividing a surface of a thermo-electric cooler into a plurality of regions of substantially the same size and shape; and
supporting optical components over the thermally conductive layer.
Preferably the optical components are positioned substantially over neutral regions in said surface. Neutral regions are described in more detail below.
The invention is also directed to a method by which the described apparatus operates and including method steps for carrying out every function of the apparatus.